Detergent slurry process

ABSTRACT

Detergent compositions are produced by heat-drying a slurry containing small crystals of sodium tripolyphosphate hexahydrate. The small crystals are formed by dispersing anhydrous sodium tripolyphosphate in water prior to its hydration with the water and subsequently other constituents of the composition are admixed with the slurry. An apparatus for forming detergent slurries is described.

0 United States Patent [151 3,639,288 Kerkhoven et al. Feb. 1, 1972 541 DETERGENT SLURRY PROCESS [56] References cm [72] Inventors: Frederik Johan Kerkhoven; Seyer Troost, UMTED STATES PATENTS both of Vlaardingen, Netherlands 1 3,174,934 3/l965 Shen ..252/l3$ 1 Asslgneez y Brothers p y New York. 3,133,024 5/1964 Feierstein et al. ..252/13s N. Primary Examiner-Leon D. Rosdol [22] Ffled' 1968 Assistant Examiner-Dennis L, Albrecht [21] Appl. No.: 714,523 Attorney-Louis Kline, Jr.

[30] Foreign Application Priority Data [57] ABSTRACT I Detergent compositions are produced by heat-drying a slurry Mar. 21, Netherlands containing small crystals of Sodium p yp p ahydrate. The small crystals are formed by dispersing an- [52] [1.8. CI yd ip yp p in water prior to its y 252/137 252/138 tion with the water and subsequently other constituents of the [5 1] ll ll. Cl ..Clld 3/06,Cl id 11/02 composition are admixed with the Shiny An apparatus for [38] Field of Search ..252/ 109, l 10, 135, 137, 138; forming detergent Slunies i5 described 3 Claims, 2 Drawing Figures PATENTED FEB I I972 SHEEI 2 0F 2 DETERGENT SLURRY PROCESS The invention relates to detergent compositions and in particular to a process and apparatus for preparing heat-dried detergent compositions containing sodium tripolyphosphate.

Heat-dried detergent compositions containing sodium tripolyphosphate are conventionally made by firstly preparing a fluid mixture of water, surface-active agents and usually inorganic salts, adding sodium tripolyphosphate to this mixture and subsequently heat-drying the resulting slurry, for example by spray-drying. Due to fluctuations in the quality of commercial sodium tripolyphosphates, mainly in their fast hydrating Form I and slower hydrating Form ll content, but also in their moisture, trace metal and other phosphates content, and in their specific surface area, etc., there are often undesired variations in their processing and consequently in the uniformity of the resulting products. Additionally, unpredictable changes in slurry viscosity, caused by variations in the hydration characteristics of the sodium tripolyphosphate used, give difficulties in the subsequent heat-drying.

The different hydration characteristics of different sodium tripolyphosphates can also give wide variations in the proper ties of the heat-dried detergent compositions prepared from them. Thus, the application of conventional slurry-making techniques when using sodium tripolyphosphate with a high, fast hydrating, Form l content can allow the formation of hard lumps, commonly termed grit, in the slurries which cause blockages in pipes, filters and spraying nozzles. It has been proposed to overcome the difficulties caused by grit formation by using higher temperatures for hydration, i.e., temperatures above about 75 C., e.g., 90 C., at which temperatures the hydration of Form l sodium tripolyphosphate is believed to be slower. This delayed hydration, coupled with the relatively high solubility in water of Form l sodium tripolyphosphate is believed to result in the formation of large crystals of sodium tripolyphosphate hexahydrate in the slurry.

This method and others proposed, suffer from one general disadvantage in that they are specific to the use of a particular quality of sodium tripolyphosphate or to the production of a particular type ofdetergent composition, or to both. 5

It has now been found, in accordance with this invention, that the difficulties due to variations in sodium tripolyphosphate quality can be decreased and that detergent compositions with improved physical properties can be obtained if the anhydrous sodium tripolyphosphate is substantially homogeneously dispersed in water and thereafter hydrated to form a large number of small sodium tripolyphosphate hexahydrate crystals, substantially all of which have a maximum dimension of not greater than 100p, prior to the admixture of other detergent slurry constituents. The slurry is subsequently heat-dried, for example by spraydrying, to give a detergent composition.

Generally speaking, the smaller the size of the sodium tripolyphosphate hexahydrate crystals the better the physical properties of the resultant composition. The sodium tripolyphosphate hexahydrate crystals should have a maximum dimension of not greater than 100/1. as larger crystals are apt to impart crawly flow properties to the dried compositions, especially in the case of compositions of the mixed active type containing a nonionic surface-active agent. in some particularly difficult cases crawly powder properties may even be obtained with a crystal size of less than 100p. and it is preferred in these cases, and generally, to operate the process of the invention so as to obtain crystals having as small a crystal size as possible, preferably not more than about 50p" Such a small size for substantially all of the crystals of sodium tripolyphosphate hexahydrate in a detergent composition has not been commercially attainable hitherto and the invention includes, in one aspect, a detergent composition containing sodium tripolyphosphate hexahydrate crystals substantially all of which have a maximum dimension ofnot more than 50 The small sodium tripolyphosphate hexahydrate crystals formed in the process of the invention can be produced from any commercial quality of anhydrous sodium tripolyphosphate, whether of high Form l or of high Form ll content, provided that the sodium tripolyphosphate is substantially homogeneously dispersed in the water prior to hydration. This dispersion is preferably performed using intensive stirring. it will be appreciated that the anhydrous sodium tripolyphosphate should be in powder form to enable the dispersion to be achieved.

The operating temperatures for the dispersion of the anhydrous sodium tripolyphosphate in the water and for its subsequent hydration are chosen according in particular to the type of sodium tripolyphosphate used, the type of apparatus employed for both operations, the other components, if any, in the water of dispersion and the crystal size desired in the product. For economic reasons it is desirable to use both for dispersion and hydration temperatures in the region of ambient temperature and it is an important beneficial feature of the present invention that this may be achieved while obtaining high-quality products. 1

in order to disperse substantially homogeneously the anhydrous sodium tripolyphosphate in the water prior to its hydration it is preferred to use intensive stirring at the point of their first contact. An apparatus found to be highly effective for accomplishing this is a nonrecirculatory, intensively stirrable device for example a disc-rotor pump which has the advantage of having a small holdup. The subsequent hydration of the dispersed sodium tripolyphosphate can be accomplished in less intensively stirred vessels, for example in a Lang disintegrator mixer. Using sufficiently rapid dispersion of the anhydrous sodium tripolyphosphate in the water it is possible to form the desired small crystals of the hexahydrate from all commercially available types of anhydrous sodium tripolyphosphate at temperatures of around ambient temperature, that is within the-region of from about l5 to 45 C., preferably from about 20 to 25 C.

On the treatment of some types of anhydrous sodium tripolyphosphate particularly those having a high Form l content, it may be desirable to use higher or lower temperatures than about ambient temperatures. At these higher or lower temperatures it is believed that the rate of hydration is decreased so enabling dispersion to be accomplished more readily before hydration has commenced to any appreciable extent. Thus, for example, it has been found possible to obtain small crystals from sodium tripolyphosphate of high Form l content using temperatures for dispersion and hydration of about 70 C. or higher.

in the event that an intensively stirrable device is not used for dispersing the anhydrous sodium tripolyphosphate in the water, for example if it is desired to use a crutcher mixer for this operation, the rate of hydration should be lowered, usually by the use of temperatures higher or lower than ambient temperatures, so as to allow dispersion to be achieved before hydration. This is particularly important in the case of anhydrous sodium tripolyphosphate with a high content of fast-hydrating Form l material. It has been found that the process of the present invention can be accomplished in crutcher mixers using water temperatures as low as from about 0 to 15 C. After the substantially homogeneous dispersion has been formed at these low temperatures hydration should be allowed to occur by raising the temperature, preferably to within from about 15 to 45 C. At these temperatures it is believed that hydration proceeds at a maximum rate, which is conducive to the production of small crystals.

The use of water to form the dispersion of the anhydrous sodium tripolyphosphate is an essential feature of the present invention. This enables dispersion of the sodium tripolyphosphate to be accomplished before hydration, which would be prevented by the presence of major quantities of other ingredients in the water, and is so prevented in conven-' tional slurry-making processes in which the anhydrous sodium tripolyphosphate is the last component to be added to the slurry and in which relatively large sodium tripolyphosphate crystals are thereby formed. in order to obtain large numbers of small crystals as required it is desirable to have hydration occur at a high rate. This is achieved to some extent by using a temperature within the range of from about to 45 C., as mentioned above, but is considerably helped by the use of water for the previous dispersion of the anhydrous sodium tripolyphosphate as this enables the rapid production of a supersaturated solution of the sodium tripolyphosphate from which crystals are subsequently formed most rapidly.

The ratio of the water to the anhydrous sodium tripolyphosphate used in the processeffects to some extent the size of the sodium tripolyphosphate crystals produced. Generally speaking, it is advantageous to use as little water as possible, as this encourages theformation of solutions having high levels of supersaturation, and .hence aids in the production of small hexahydrate crystals.

It is to be understood that the water used for dispersion of the anhydrous sodium tripolyphosphate may contain minor amounts of other constituents of the detergent composition to be produced, for example up toabout percent by weight of other constituentsThis is, of course, appreciably less than the proportion of nonaqueous constituents in conventional aqueous slurries before addition of the I anhydrous sodiu tripolyphosphate.

It has been found that the presence of sodium silicates (water-glass) in the water used for dispersion of the sodium tripolyphosphate is beneficial. Additionally, an anionic surface-active agent, for example soap, may advantageously be added to the water used to form the dispersion of the sodium tripolyphosphate or to the dispersion itself prior to hydration. The use of both the silicates and the anionic surfactant appear to aid the formation of small crystals of the sodium tripolyphosphate hexahydrate and the presence of the latter improves the handling properties of the slurry.

The process according to the invention is particularly advantageous in that it enables the production of detergent compositions having good physical properties, irrespective of the type of detergent active material or mixtures thereof used. For example, the process of the invention is beneficial in preparing low-sudsing, ternary active compositions which contain synthetic anionic surface-active agents, nonionic surface-active agents and soaps, which are recognized as being particularly difficult to manufacture with good physical properties. Hitherto, it has been very difficult to produce a noncaking powder based on these mixed active systems, especially those which contain a relatively large amount of the nonionic constituent.

An additional advantage of the process according to the invention is that it can be applied successfully to all commercial qualities of anhydrous sodium tripolyphosphate. Further, process conditions may be chosen to suit a variety of different qualitiesof sodium tripolyphosphate so that the process may be operated without the frequent changes of conditions otherwise necessary.

The process of the invention is readily adaptable to the continuous preparation of detergent slurries for subsequent heatdrying but is also suitable for batchwise operation. Preferably, however, the anhydrous sodium tripolyphosphate is dispersed in the water continuously, the hydration of the sodium tripolyphosphate and the subsequent admixing of the other constituents being operable on either a continuous or a batchwise basis.

In a further aspect the invention comprises an apparatus for the preparation of a slurry for heat-drying to form a detergent composition, comprising a nonrecirculatory, intensively stirrable device, dosing systems for continuously feeding water and anhydrous sodium tripolyphosphate to the intensively stirrable device so as to disperse substantially homogeneously the sodium tripolyphosphate in the water, a stirrable vessel adapted to receive the dispersion of sodium tripolyphosphate in water from the intensively stirrable device and means for feeding other ingredients of the detergent composition to the stirrable vessel.

Two embodiments of apparatus according to the invention are illustrated, by way of example, in the accompanying diagrammatic drawings of which FIG. 1 shows a continuously operable slurry-making apparatus while the apparatus in FIG. 2 is adapted for batchwise operation.

In the Figures like numbers denote like parts. I In both Figures a disc-rotor pump 1, having a motor la, a rotatable disc lb and a hopper 1c is supplied with water through a pipe 2, the flow through which is controlled by a valve 3 and a flowmeter 4. A hopper 5 is positioned over an endless belt 6 for feeding anhydrous sodium tripolyphosphate to the disc-rotor pump 1. A pipe 7 connects with the pipe 2 for feeding any additional liquid materials to the disc-rotor pump.

An output pipe 8 from the disc-rotor pump I leads into a Lang disintegrator mixer 9, comprising an open top vessel 9a, an impeller 9b and a motor 90. A further pipe 10 leads into the Lang mixer for the addition thereto of any additional materials. The output pipe 11 from the Lang mixer 9 is controlled by a valve 12 and leads to a pump 13 and thence to apparatus which is different in the two Figures. I v

In FIG. 1 the pipe 11 from the Lang mixer 9 leads'into a second Lang disintegrator mixer 14, having an open top vessel 14a, an impeller 14b and a motor 14c. An additional pipe 15 also leads into the second Lang mixer 14 for supplying thereto any other liquid constituents of detergent compositions being prepared. Further means (not shown) may be provided for adding any solid slurry constituents to the Lang mixer 14. The output pipe 16 from the second Lang mixer 14 is controlled by a valve 17.

In FIG. 2 the pipe 11 from the Lang mixer 9 leads to two crutcher mixers l8 and 19, each having an open tope vessel, 18a and 19a and an impeller 18b and 19b, respectively (the means for rotating the impellers is not shown). The flow from the pipe 11 to the crutcher mixers l8 and 19 is controlled, respectively, by valves 20 and 21. A further pipe 22 leads to the crutcher mixers l8 and 19, for supplying any other liquid slurry constituents to the mixers, as controlled by valves 23 and 24, respectively. Further means (not shown) may be provided for adding any other solid slurry constituents to the mixers. The outputs from the crutcher mixers, 18 and 19 are controlled by valves 25 and 26, respectively, connecting with a common pipe 27.

In operationpowdered anhydrous sodium tripolyphosphate is fed to the disc-rotor pump 1 from the belt 6 at a constant rate while water, containing any desired additives such as silicates from the pipe 7, is fed to the disc-rotor pump through the pipe 2. In the discrotor pump the sodium tripolyphosphate is very rapidly dispersed in the water before any substantial degree of hydration can take place. The dispersion of the sodium tripolyphosphate in the water is fed to the Lang mixer 9, to which any other desired additive, for example soap, is fed through the pipe 10. Hydration occurs to some extent in the Lang mixer. The slurry so formed is then fed either to the second Lang mixer 14 in FIG. 1 or to one or other of the crutcher mixers 18 and 19 in FIG. 2. The other ingredients of the slurries are fed through the line 15 in FIG. 1 or the line 22 in FIG. 2 to the final mixing vessels so as to produce, in the apparatus shown in FIG. 1 in a continuous stream of slurry and in the apparatus shown in FIG. 2 a series of batches of slurry from alternate crutcher mixers, which are discharged to heat-drying apparatus through the lines 16 and 27 in FIGS. 1 and 2 respectively.

Using the apparatus described above, with the addition of sodium silicate to the water prior to dispersion and of soap to the dispersion, it has been found possible to form homogeneous grit-free slurries containing large'numbers of small crystals of completely hydrated sodium tripolyphosphate. In the apparatus described above the slurries so formed have intermittently or continuously admixed with them the other constituents of the detergent compositions for their subsequent heat-drying. However, it has been found that the slurries prior to such admixture of the other constituents are stable even on prolonged storage and the process may be operated with a considerable delay between initial hydration and subsequent admixture and heat-drying if desired. For the final heat-drying it is usual to heat the slurry to about 70-80 C. or higher, which temperature may be used for the admixture of the other detergent constituents if desired. The final slurry is of excellent and stable consistency for pumping and spraying in the heat-drying process.

A large variety of detergent compositions can be prepared by the process of the invention, including those containing anionic and/or nonionic and/or even amphoteric substances as the detergent active agent or agents. These detergent active agents, which are generally compatible with sodium tripolyphosphate, include for example soaps (i.e., the sodium and/or potassium salts of long chain fatty acids, water-soluble alkylaryl sulphonates, such as sodium dodecyl benzene sulphonate and sodium tetradecyl benzene sulphonates, water-soluble alkane and alkene sulphonates, alkyl sulphates obtained for example by sulphation of aliphatic alcohols with branched or unbranched alkyl chains, including sodium lauryl sulphate, sodium hexadecyl sulphate and sodium octadecyl sulphate, alkali salts of sulphated or phosphated alkylene oxide condensation products prepared by ethoxylation and/or propoxylation and subsequent sulphation or phosphation or various organic hydrophobic compounds containing active hydrogen, such as alcohols, mercaptans and alkyl phenols, sodium alkyl glycerol ethers, including for example sodium fatty acid monoglycerides sulphate, alcohol alkylene oxide condensation products, alkylphenol-alkylene oxide condensation products prepared for example by condensing an alkyl phenol with ethylene oxide and/or propylene oxide, and the like.

The above substances, either separately or in combination, may form the active detergent components of the detergent composition of the invention. The detergent compositions may additionally contain other conventional additives, including for example various fillers, alkaline substances, soilsuspending' agents, bleaching agents, optical brighteners, coloring agents, germicides, perfumes and lather boosters.

Embodiments of the invention are illustrated by the following examples in which parts and percentages are by weight:

EXAMPLE I water waterglass [35% solution. Na O:SiO- .=l:2)

was supplied to a Landustrie disc-rotor pump at a flow rate of 3.57 kg./min. and at a temperature of 20 C. Using 'a powder dosing belt conveyor, 1.88 kgJmin. of anhydrous sodium tripolyphosphate (containing less than 10 percent Form I) were also continuously dosed to the disc-rotor pump which for this purpose had an upright powder and solution inlet.

The resultant sodium tripolyphosphate dispersion was fed from the pump to a 30 liters capacity stirred tank which each time it became filled was emptied and its contents poured into a larger stirred tank of 1,000 liters capacity. When the required slurry content had accumulated in the larger tank, the slurry was heated and the contents of the tank made up to about 1,000 liters with the following:

kg. alkyl benzene sulphonate paste (40% active) 75.6 nonyl phenol-l4 EO 31.8 soap carhoxymethyl cellulose (40% active) 14.0 Nix- S0 60.0

After mixing for 5 minutes at 70 C., an excellent slurry was obtained containing sodium tripolyphosphate hexahydrate crystals of about 20-40 .L. On spray-drying this slurry a noncaking and free-flowing detergent composition of excellent structure was obtained.

EXAMPLE II An aqueous sodium silicate solution and powdered anhydrous sodium tripolyphosphate (of 20 percent Form l content) were continuously dosed to a disc-rotor pump arranged as in example l. The aqueous solution had the composition:

Pans

water l0 waterglass (25"; solution, Na .O:SiO l :14) l The feed rates for the aqueous solution and the sodium tripolyphosphate were 11 kg./min. and 7.5 kg./min. respectively. The latter contained three parts of soap per parts of sodium tripolyphosphate. The output from the disc-rotor pump was fed to a slowly stirred tank of 1,000 liters capacity, from which the resultant slurryof sodium tripolyphosphate hexahydrate crystals was continuously withdrawn and pumped into a further stirred mixing tank until 420 kg. of slurry had been so obtained. To this slurry of hexahydrate crystals (size about 20-40;.t) were added the following:

. kg. tallow fatty alcohol-25 E0 250 carboxymethyl cellulose 8.5 Na. .SO, I60

The resultant mixture was heated to 80 C. and pumped to a spray-drying plant from which it was spray-dried to give a freeflowing, crisp, dry detergent composition having no tendency to caking.

EXAMPLE ill Water and. alkaline waterglass (33 percent solution, Na O:SiOhd 2=l 1.8) were mixed in a ratio of 42.2:87,8 parts, respectively.

The resultant solution was continuously fed at 20 C, and at a rate of about 7 kg./min, to a disc-rotor pump. Anhydrous sodium tripolyphosphate (about 30 Form 1) was also fed to the disc-rotor pump at a rate of 4.13 kg./min. In addition, a separate flow of alkyl benzene sulphonate paste was fed to the disc-rotor pump at a rate of 3.0 kg./min. After 45 minutes the flows of material to the disc-rotor pump were stopped and the resultant mixture which had been fed to a stirred mixing tank was made up with the following:

kg. alkyl benzene sulphonate paste (405 active) 3 l0.0 coconut fatty acid ethanolamidc l8.5 carboxymethyl cellulose l5.0 Na SO 73.0 optical brighteners 0.52

The slurry thus obtained contained sodium tripolyphosphate crystals of approximately 20-40,:t.

A detergent composition prepared by spray-drying the slurry was free-flowing and showed no tendency to caking.

EXAMPLE IV A continuous flow of an aqueous sodium silicate solution having the composition:

water waterglass (35% solution, NaO:SiO- -=l:2)

of which about 40 liters were occupied by the dispersion. Hydration of the sodium polyphosphate in this mixer was substantially completed within 3 minutes and the crystallized mass was continuously discharged into stirred slurry-mixing vessel to which the following addition constituents were continuously added:

. kgJmin. alkylbenzenesulphonate paste (427: active) 3.8 tallow fatty acid amide-l 1 EO 0.7 stearic acid 0.4 sodium hydroxide solution (33% 0.2 carboxy methyl cellulose 0.2 sodium carbonate 0.3 magnesium sulphate 0.2 sodium sulphate 0.6 ethylene diamine tetraacetic acid 0.03 optical bleach 0.04

The resultant detergent slurry was continuously pumped to a tower from which it was spray-dried to give a detergent composition which contained sodium tripolyphosphate hexahydrate crystals of about 20-30;; in size. The composition was exceptionally free-flowing, dry and had a good appearance.

For purposes of comparison, to demonstrate the advantages of having small sodium tripolyphosphate hexahydrate crystals, two further compositions were prepared containing hexahydrate crystals larger than 20-30 4, but substantially identical in constitution with the composition prepared as described above.

One such composition which was prepared by a process of the invention had hexahydrate crystals of 50-70;.t. This composition had a satisfactory appearance but was less free-flowing than the composition of 20-30;. crystal size, although still acceptable.

A further composition having the same constitution was prepared by a conventional process. The hexahydrate crystal size range in the composition was about 80-l 10p. and the composition had crawly" flow properties instead of being free flowing and it felt rather sticky.

As a general rule it has been found that detergent compositions of the low-sudsing type containing termary mixtures of I detergent active compounds, as with the compositions described above, should contain sodium tripolyphosphate hexahydrate crystals the size of substantially-all of which is not more than about IOO for them to be acceptable.

What is claimed is: I v

l. A process for preparing a detergent slurry containing sodium tripolyphosphate hexahydrate crystals of a size not exceeding 100p. for spray drying to form a built detergent composition which comprises forming a substantially homogeneous dispersion of anhydrous sodium tripolyphosphosphate in water at a temperature between about C. to about l C. without appreciable hydrationvoccurring by blending the anhydrous sodium tripolyphosphate in powder form with water containing up to about 30 percent of sodium silicates using intensive stirring provided by a disc-rotor pump at the'point of their first contact, allowing said dispersion of sodium tripolyphosphate to hydrate to the hexahydrate in said temperature range to form a slurry and thereafter mixing an organic surface active agent with the slurry.

2. A process for preparing a heat-dried built detergent composition containing sodium tripolyphosphate hexahydrate crystals of a size not exceeding p. which comprises forming substantially homogeneous dispersion of anhydrous sodium tripolyphosphate in water at a temperature between 0 C. to.

about 15 C. without appreciable hydration occurring by blending the anhydrous sodium tripolyphosphate in powder form with water containing up to about 30 percent of sodium silicates using intensive stirring provided by a disc-rotor pump at the point of their first contact, allowing said dispersion of sodium tripolyphosphate to hydrate to the hexahydrate in said temperature range to form a slurry and thereafter mixing an organic surface active agent with the slurry and spray-drying said slurry;

3. The process according to claim 2, wherein the size of the sodium tripolyphosphate hexahydrate crystals is not more than 50;!"

PO-ww UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 3,639,288 Dated r ar 1, 1972 Inventor) Frederik Johan Kerkhoven and Seyer Tr o t It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 5, line 22, secOnd occurrence should read f Column 6,- line- 9, "25%" should be 35%--;

line 10, "Na O:SiO =.l':3.4" should be on line 9-;

same line, "42. 2: 87,8 should be --42.2:87.8-;

line 4-0, "30" should be --30%-;

Column 7, line 2, "polyphosphate'Y should be -tripoly.phosphate-- Signed and sealed this 26th day of September 1972.

(SEAL) Attest:

EDWARD M.FLETCHER ,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents 

2. A process for preparing a heat-dried built detergent composition containing sodium tripolyphosphate hexahydrate crystals of a size not exceeding 100 Mu which comprises forming substantially homogeneous dispersion of anhydrous sodium tripolyphosphate in water at a temperature between 0* C. to about 15* C. without appreciable hydration occurring by blending the anhydrous sodium tripolyphosphate in powder form with water containing up to about 30 percent of sodium silicates using intensive stirring provided by a disc-rotor pump at the point of their first contact, allowing said dispersion of sodium tripolyphosphate to hydrate to the hexahydrate in said temperature range to form a slurry and thereafter mixing an organic surface active agent with the slurry and spray-drying said slurry;
 3. The process according to claim 2, wherein the size of the sodium tripolyphosphate hexahydrate crystals is not more than 50 Mu . 